1. Technical Field of the Invention
The present invention relates to improvements in the processing of material, in particular to improvements in the batch processing of waste to produce syngas or other combustible gasses.
2. Description of the Related Art
The batch processing of material, such as waste, using ovens is documented in the prior art, in particular in patent application WO2006/100512 in the name of Perry et al.
In such methods of material processing, waste material is heated in a large rotating oven in a reduced oxygen environment such that organic components thereof either paralyse or gasify to produce a combustible gas.
This gas is then channelled, via a conduit, into a treatment chamber wherein the temperature of the gasses are raised. In the treatment chamber, the produced gasses may either be incinerated so as to produce a hot exhaust gas from which an energy may be recovered, for example in heat exchange of a boiler, or alternatively the produced gasses may be heated without combusting them to destroy any volatile organic compounds (VOC's) therein, and the resultant synthesis gas, commonly referred to as syngas, can then either be used directly or stored for future use, for example in a syngas engine.
Such apparatus can be used for the treatment of any material containing organic materials, for example biomass, industrial waste or unusable solid waste. Such materials frequently have a high moisture content and, although this does not prevent the process from working, produces its efficiency as, prior to the temperature of the material being processed reaching a temperature at which gasification can occur, the moisture must be driven off from the material. As water has an evaporation temperature of 100° C., the temperature of the material being processed is maintained at a low temperature for a substantial amount of time while the water is driven off prior to gasification or pyrolysis beginning.
Depending on the process parameters, in particular of whether gasification or pyrolysis is occurring, it may be necessary to add water to the system later in the process to produce steam. During a pyrolysis process there is substantially no oxygen present within the system. Accordingly, the carbon released from the material being processed is not burnt and exists in the oven and gas stream as soot. This is partially mitigated by the soot reacting with water released from the material as it is being processed as it reacts, at temperature, with the soot to produce hydrogen and carbon monoxide. However the water release from the material being processed is variable and unpredictable.
It is a purpose of the present invention to, at least in part, mitigate some of the abovementioned problems.